1. Field of the Invention
The present invention relates to a method for compensating a mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter, and more particularly, to a method for compensating gain mismatch/phase mismatch/path delay mismatch of an in-phase signal and a quadrature signal of a receiver or a transmitter.
2. Description of the Prior Art
In a conventional zero-IF (zero intermediate frequency) receiver, a radio frequency signal can be directly converted into a baseband signal. Because there is no middle frequency required to be selected, the image frequency interference of a super-heterodyne receiver will not be happened in the zero-IF receiver, and the zero-IF receiver does not need a high quality filter. In addition, because the zero-IF receiver includes only one local oscillator (i.e. only one phase noise source), the zero-IF receiver does not need large and expensive filter, and can be simply integrated. However, in the zero-IF receiver, the in-phase signal and the quadrature signal may have I/Q mismatch issue because the oscillation signals supplied to the in-phase channel and the quadrature channel are not matched. In addition, because the path delays of the in-phase channel and the quadrature channel may be different, the in-phase signal and the quadrature signal may also have the path delay mismatch issue.
Because the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal and the quadrature signal may influence the following signal processing operation (e.g., the bit error rate (BER) increases), how to design a method for estimating and compensating the gain mismatch/phase mismatch/path delay mismatch of the in-phase signal and the quadrature signal is an important topic.